Thanks Fabrice.  After more experimentation, I found that image-converter
field of the customization alist should be:

("dvipng -fg %F -bg %B -D %D -T tight -o \"%o%b\.png\" %f")

If this also works for *nix, then I hope that the org-mode maintainers will
make this string the new default.  If it doesn't work on linux, then I hope
that it's possible to come up with a string that works in both OS families
(and that could be the new default).  I'll be back on Linux in a few
months, and would love to keep a simple, cross-platform .emacs file.

On Sat, Nov 26, 2016 at 5:35 PM, Fabrice Popineau <
fabrice.popineau@supelec.fr> wrote:

>
>
> 2016-11-26 16:41 GMT+01:00 Scott Otterson <scotto@sharpleaf.org>:
>
>> In my Windows build of emacs, when I put the cursor in a latex equation
>> and run
>>
>> M-x org-toggle-latex-fragment
>>
>>
>> then things chug along for a second but then fail.  In the *Org Preview
>> LaTex Output* buffer, I see the message:
>>
>> This is dvipng 1.15 Copyright 2002-2015 Jan-Ake Larsson
>> [1
>> dvipng: Fatal error, cannot open output file
>> c:/Users/scott/AppData/Local/Temp/"orgtex4628hQG.png
>>
>>
>> The reason for the failure is the leftover quote (...Temp/"orgtex...) in
>> the expected png output file.  With some hackery, I can see that the
>> command that's being run is:
>>
>> dvipng -fg "rgb 0 0 0" -bg "rgb 1 1 1" -D "102.0" -T tight -o
>> "c:/Users/scott/AppData/Local/Temp/""orgtex4628hQG".png
>> "c:/Users/scott/AppData/Local/Temp/orgtex4628hQG.dvi"
>>
>>
>> If I paste that into a cygwin xterm, it runs fine on the .dvi file that's
>> still in the Temp directory.  But the command fails in a Windows cmd
>> window; if I remove the extra quotes, then the command works in the cmd
>> window too.
>>
>> The extra quote comes from the default customization for the dvipng
>> image-converter field of org-preview-latex-process-alist:
>>
>> dvipng -fg %F -bg %B -D %D -T tight -o %o%b.png %f
>>
>>
>>
> This command should read :
>
> dvipng -fg %F -bg %B -D %D -T tight -o "%o%b.png" %f
>
> and the args shouldn't be quoted before.
> Unquoting those strings will possibly require to change other command
> strings.
>
> Fabrice
>